1. Field of the Invention
This invention relates to a motive force (power) control system for a vehicle equipped with an internal combustion engine and an automatic transmission, particularly to a vehicle motive force control system that optimizes vehicle fuel economy by integrated control of the engine and the automatic transmission.
2. Description of the Prior Art
In a motor vehicle equipped or configured according to the prior art, when the vehicle operator depresses the accelerator pedal to raise the engine speed so as to accelerate the vehicle, since the generated motive force is initially consumed to increase the inertia force (torque and moment) of the automatic transmission and the vehicle body, the motive force can not immediately be attained as desired. On the contrary, when the operator releases the pedal from the depressed position to decelerate the vehicle, since the inertia force does not decrease immediately, the motive force becomes larger than desired. These factors degrade not only fuel economy performance, but also drivability.
In order to solve this problem, Japanese Laid-Open Patent Application No. Sho 63(1988)-232,043 teaches controlling the gear ratio on the basis of predetermined characteristics satisfying an improvement of fuel economy and, if the accelerator pedal is depressed to accelerate, controlling the gear ratio without using the characteristics to determine the desired engine speed, thereby achieving smooth acceleration so as to faithfully meet the operator's desire. Moreover, Japanese Patent Publication No. Hei 6(1994)-65,529 and Japanese Laid-Open Patent Application No. Hei 6(1994)-129,273 propose limiting the engine output to absorb inertia torque during gear shifting.
The prior art mentioned in Japanese Laid-Open Patent Application No. Sho 63(1988)-232,043, is disadvantageous, however, in that it disregards fuel economy characteristics when the vehicle accelerates, degrading fuel economy performance. The prior art described in Japanese Patent Publication No. Hei 6(1994)-65529 and Japanese Laid-Open Patent Application No. Hei 6(1994)-129,273 limits the engine torque, not for improving fuel economy performance, but for reducing shock generated during gear shifting, and teaches nothing regarding adjustments for the response delay due to the inertia torque so as to enhance fuel economy performance and drivability during vehicle acceleration or deceleration.